The singer and husband Brandon Blackstock announced she was pregnant not long after their October 2013 wedding.

Clarkson, who is four months along, announced the sex of the baby on Twitter on Monday.

"We just found out we're having a girl officially! I knew it! Only a girl could cause this much drama with all this vomiting ha!" she wrote.

The Tie It Up star is clearly over the moon about her news, despite the morning sickness. Clarkson made several comments in the past about how much she hoped the baby would be a girl.

"I'm totally gonna have a girl. I'm manifesting it! And when I have a girl, you're gonna be like, 'That chick knew it!'" she told Parade magazine in November 2013.

The 31-year-old admitted she has not had an easy pregnancy so far.

According to the star, carrying a baby is nothing like she expected it to be.

"I vomit a dozen times a day. It's like bad. I vomited before coming out here," she revealed on the Ellen DeGeneres Show. "It's so bad. It's, like, so gross. You're not attractive when you're pregnant. Everybody tells you [that] you glow and your hair is pretty and your nails are pretty. That's total crap.

"My nails are short, my hair still falls out - it's not all lush and beautiful - and I have no glow. Unless it's, like, something left over from a bad throw up. It's horrible."